1. Field of the Invention
The present invention relates to a raw material composite for a carbon material used in an electric double layer capacitor and a manufacturing method of the same, and to an electric double layer capacitor and a manufacturing method of the same.
2. Related Background Art
In the past, based on a concept that a capacitance of an electric double layer capacitor is approximately in proportion to the surface area of polarizable electrodes (such as carbon electrodes) configured as an anode and a cathode constituting the electric double layer capacitor, various considerations have been made to increase the surface area of a carbon material for the carbon electrodes in order to increase the capacitance thereof when using the carbon electrodes as the polarizable electrodes.
For example, activated carbon has been heretofore used as the carbon material for the carbon electrodes. A method including the steps of carbonizing a raw material for the carbon material (hereinafter referred to as “raw material carbon”) at a temperature of 600° C. or below, and then subjecting a carbonized intermediate product thus obtained (hereinafter referred to as a “raw material composite”) to an activation treatment, has been known as a method for increasing the specific surface area of this activated carbon.
As for this activation treatment, there are known a method of heating the raw material composite in a temperature range from 600° C. to 1000° C. in a water vapor or carbon dioxide atmosphere or a method of mixing zinc chloride, potassium hydroxide or the like with the raw material composite and then heating in an inert gas atmosphere, and the like. In the course of this activation treatment, numerous pores suitable for absorption are formed on the surface of the material to constitute the activated carbon, and the specific surface area of the activated carbon is resultantly increased. The specific surface area of the activated carbon thus manufactured accounts for a range from 1000 to 2500 m2/g or thereabouts, for example, when measured by the nitrogen gas absorption method (the BET method).